README.md
1# Fuzzers for libkeymaster4
2
3## Plugin Design Considerations
4The fuzzer plugins for libkeymaster4 are designed based on the understanding of the
5source code and try to achieve the following:
6
7##### Maximize code coverage
8The configuration parameters are not hardcoded, but instead selected based on
9incoming data. This ensures more code paths are reached by the fuzzers.
10
11libkeymaster4 supports the following parameters:
121. Security Level (parameter name: `securityLevel`)
132. Padding Mode (parameter name: `paddingMode`)
143. Digest (parameter name: `digest`)
154. Key Format (parameter name: `keyFormat`)
165. Key Purpose (parameter name: `keyPurpose`)
17
18| Parameter| Valid Values| Configured Value|
19|------------- |-------------| ----- |
20| `securityLevel` | 0.`SecurityLevel::SOFTWARE` 1.`SecurityLevel::TRUSTED_ENVIRONMENT` 2.`SecurityLevel::STRONGBOX`| Value obtained from FuzzedDataProvider|
21| `paddingMode` | 0.`PaddingMode::NONE` 1.`PaddingMode::RSA_OAEP` 2.`PaddingMode::RSA_PSS` 3. `PaddingMode::RSA_PKCS1_1_5_ENCRYPT` 4.`PaddingMode::RSA_PKCS1_1_5_SIGN` 5.`PaddingMode::PKCS7`| Value obtained from FuzzedDataProvider|
22| `digest` | 1. `Digest::NONE` 2.`Digest::MD5` 3.`Digest::SHA1` 4.`Digest::SHA_2_224` 5.`Digest::SHA_2_256` 6.`Digest::SHA_2_384` 7.`Digest::SHA_2_512`| Value obtained from FuzzedDataProvider|
23| `keyFormat` | 1. `KeyFormat::X509` 2.`KeyFormat::PKCS8` 3.`KeyFormat::RAW`| Value obtained from FuzzedDataProvider|
24| `keyPurpose` | 1. `KeyPurpose::ENCRYPT` 2.`KeyPurpose::DECRYPT` 3.`KeyPurpose::SIGN` 4. `KeyPurpose::VERIFY` 5. `KeyPurpose::WRAP_KEY`| Value obtained from FuzzedDataProvider|
25
26This also ensures that the plugins are always deterministic for any given input.
27
28##### Maximize utilization of input data
29The plugins feed the entire input data to the module.
30This ensures that the plugins tolerate any kind of input (empty, huge,
31malformed, etc) and dont `exit()` on any input and thereby increasing the
32chance of identifying vulnerabilities.
33
34## Build
35
36This describes steps to build k4_AndroidKeymaster4Device_fuzzer binary
37
38### Android
39
40#### Steps to build
41Build the fuzzer
42```
43 $ mm k4_AndroidKeymaster4Device_fuzzer
44```
45#### Steps to run
46To run on device
47```
48 $ adb sync data
49 $ adb shell /data/fuzz/${TARGET_ARCH}/k4_AndroidKeymaster4Device_fuzzer/k4_AndroidKeymaster4Device_fuzzer
50```
51
52## References:
53 * http://llvm.org/docs/LibFuzzer.html
54 * https://github.com/google/oss-fuzz
55